The invention relates to a system for grinding the optical surfaces and/or the edges of eyeglass lenses using a grinding disk, a rotatable holder for an eyeglass lens blank and a device for controlling the grinding processes in accordance with a preselected outline for the eyeglass lens.
Eyeglass lens edge grinding machines are known in the art and can in their simplest embodiment include a device to control the grinding process in accordance with a pre-selected outline for the eyeglass lens in the form of a template mounted on a rotatable holder. This template generally corresponds to the shape of the lens opening in the frame into which the ground eyeglass lens is to be inserted.
CNC controlled eyeglass edge grinding machines are also already known in the art and are disclosed, for example, in German published, unexamined patent specification 33 16 619 or European published, unexamined patent specification 0 363 281. CNC controlled eyeglass lens grinding machines which process the optical surfaces as well are disclosed in European patent specification 0 061 918 and in German patent specification 38 17 850. In the case of the CNC controlled eyeglass lens edger machines the outline of the eyeglass lens is provided in the form of data record which is used to control the grinding process in such a way that the prescribed outline of the eyeglass lens will be achieved.
Common to both the purely mechanical and the CNC controlled eyeglass lens grinding machines is that the eyeglass lens blank is inserted in the holder by hand, which is time-consuming and which requires a certain degree of skill.
Before the eyeglass lens blank can be inserted in the rotatable holder of a conventional eyeglass lens grinding machine, the eyeglass lens blank must be fitted in advance with a sucker or block which must be positioned in accordance with the decentration values for the prescribed outline, determined by the optician, referenced to the optical center of the eyeglass lens. The block or sucker serves to hold the eyeglass lens blank exactly in position in the rotatable holder and which makes with the rotatable holder a connection resistant to rotation.
If the eyeglass blanks are to be subjected to cylindrical or prismatic grind, the angle of the axis of the cylinder (cylinder angle) must also be observed when positioning the sucker or block and when inserting the configuration in the rotatable holder in the eyeglass lens edge grinding machine.
A further difficulty is encountered where eyeglass lens blanks are manufactured as multi-focal lenses since then the location of the presbyopia correction segment with reference to the optical center of the distant vision segment will have to be observed.
To apply a sucker or block, a device is used with which the eyeglass lens blank is initially positioned in accordance with the optical value, the decentration values and/or the cylinder angle, after which the sucker or block is attached to the prepositioned eyeglass lens blank.
It is obvious that this method of operation is time-consuming and requires great professional skill so that this activity can be carried out only by trained opticians. Due to the time consuming positioning; and blocking of each eyeglass lens blank, however, the degree of utilization for the eyeglass grinding machine, particularly when it is CNC controlled, is low.
A loading device at the lens edge grinding machine disclosed in German patent 1 238 802 cannot substitute for the skill of the optician since this machine is suitable only for loading when the interpupillary distance is exactly aligned with the optical center.